Saving Lives Is a Tough Job – But a 3D-printed Variable-infill Antenna Can Do It

White powder snow glittering in the sun. Miles of slopes ahead. Anyone who’s ever skied in the Alps (or any other mountain for that matter) knows the thrill. And what thrills the alpine regions is the huge contribution that winter tourism has to their GNP. Not to mention the importance of transalpine traffic –tons of vital goods that must be transported on routes strongly exposed to avalanche danger. So, it goes without saying that to keep the skiers and transportations safe and sound, strong preventive actions are needed. Yet, avalanches kill more than 150 people worldwide every year.

While manual analysis of the snow cover, called Manual Snow Stratigraphy, is the most used and accurate technique in avalanche forecasting, it is time-consuming, restricted to small and safe areas and requires good weather conditions. Also, it is not real time and is very expensive. Therefore, it has been suggested that microwave radars installed to the ground could be a viable alternative solution. As one of Premix's purposes is to “Create a safe and ultra-connected society with functional plastics,” we are very happy to support the lifesaving SNOWAVE project led by University of Pavia and its research team members Prof. Marco Pasian, Pedro Fidel Espín-López, Lorenzo Silvestri, Prof. Massimiliano Barbolini and Prof. Fabio Dell’Acqua.

In EuCAP 2018 Pedro and Marco published a paper titled Compact 3D-printed Variable-infill Antenna for Snow Cover Monitoring (slides can be downloaded here). In this ongoing research project, a double-ridge waveguide antenna was specially designed for snow cover monitoring and manufactured by additive manufacturing.

Avalanches start when different layers of snow are piled up and start sliding due to a catalyst. This catalyst can be the weight, the liquid water content, or the type of the crystal of the snow layers, or external loads such as skiers and snowboarders. Thus, in snow cover monitoring, knowing the snow layer composition and thickness are critical parameters for the determination of avalanche probability.

In their work Marco and Pedro used PREPERM® ABS450 3D filaments to manufacture a variable infill antenna to maintain a reasonable input matching. In their case, thanks to the higher permittivity compared to conventional filaments (εr = 2-3) together with the freedom of design inherent to 3D filaments, they were able to reduce the antenna size and weight significantly compared to an alternative 3D printed antenna. The key characteristics of different antenna types they considered are presented in table 1.

In practice, compared to current solutions, the higher permittivity 3D printed antenna had quite similar dimensions, weight and performance. All in all, a very good alternative. The 300 grams of weight difference compared to the low permittivity antenna might not seem very high, but when you're loading measuring equipment into your backpack and doing several measurements each week, the weight adds up quickly.

Just imagine running a marathon with 300 grams extra weight on your feet and you can already understand the difference. Let alone if the extra weight is several times larger in size than the alternative.

We're very excited to be a part of this research project making the world a safer place and seeing concrete examples of using additive manufacturing to solve problems! We had the pleasure to meet Marco and Pedro in EuCAP 2018 and have a good discussion on the future of high εr 3D filaments in their research.

- Marco and Pedro, how do you do see 3D printing and additive manufacturing in general? And what about as a part of moving from an idea to mass production?

For the world of radio-frequency, microwave, and millimetre-wave engineering, additive manufacturing is a great opportunity. On the one hand, it allows the designing and fabricating of devices and components that would be impossible, or at least very difficult to achieve with traditional techniques. On the other hand, even for items that can be normally realized using, for example, milling techniques, additive manufacturing has already demonstrated its advantages in terms of cost and fabrication time for a number of applications. A plus not only for industries aiming at mass production, but also for R&D laboratories for rapid and effective prototyping.

- What would have been your plans if there would not have been the possibility to use high permittivity filaments?

A common possibility could have been the realization of our antenna using CNC drilling machines, thus starting from a bulk rod of material. While we expect the final device would have been comparable in terms of accuracy and performance, the cost and fabrication time would have been significantly higher. In addition, a suited drilling machine is not as available as 3D printing.

- How well did your antenna predict different snow layer thicknesses?

The antenna is designed to provide a resolution in the order of 5 cm. At the moment the antennas have been experimentally demonstrated to determine the depth of the entire snowpack, thus providing global average values for the snow density, liquid water content, etc. For the next winter season we plan to extend the experimental campaign to include relevant layer-by-layer information.

- What are the next steps in SNOWAVE? And what about your other projects?

SNOWAVE, based on the simultaneous use of three antennas, already demonstrated its working principle, and provided information about the internal structure of the snowpack with an accuracy better than 10% for the snow depth. Nevertheless, we are working to enrich the scientific content of our prototype (among others, delivering information on the single layers, and taking into account wet snowpacks) and to engineer an upgraded version able to be used by non-specialist (implementing modern touchscreens, and dedicated open-sources codes).

At the same time, we are using Premix PREPERM® filaments, in particular those with a high dielectric constant, to design and realize novel lenses for ground antennas, intended for space communications, in collaboration with the European Space Agency. Again, the availability of these filaments is crucial for rapid, and repeated prototyping.

Thanks to the higher permittivity compared to conventional filaments (εr = 2-3) together with the freedom of design inherent to 3D filaments, the size and weight of the antenna was significantly reduced compared to an alternative 3D printed antenna.

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Victor Heinänen

Business ManagerM.Sc. (Chem. Eng), B.Sc. (BA & Econ.)

My background is in chemical engineering and business development. I aim to understand my customers’ needs holistically to deliver them a best-fit solution. Even though I am in sales, I try to under-promise and over-deliver. Let’s #makehappen!

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